Answer:
A.30
Explanation:
According to Chargaff's rule there is the same number of Thymine bases as there are of adenine
so we have 120 adenine and 120 thymine
300-120-120=60
those 60 base pairs are represented by cytosine and guanine which also pair with each other according to chargaff's rule they're equal in number
60/2=30 guanine bases
